Water Pressure Objectives:
• You will learn how to create pressure.
• You will comprehend that pressure is independent of the surface area on which a water column stands.
• You will learn and understand how elevation of a water column affects the pressure at any given point.
• You will understand that water velocity does not create pressure.
• You will appreciate that, for a given flow rate, water velocity is a function of cross-sectional area and pressure is a force causing the water flow through nozzles or hill elevations.
Pressure is a little harder
to understand.
Pressure is the force that moves water through a pipe.
We will
try to explain it using a water tower and the weight of water. Think of gravitational "head" pressure -- the higher the tower, the greater the pressure. The height of a water tower creates a large elevation
difference where the weight of water in a pipe between two elevations creates
pressure.
Pressure created by a pump is a little more difficult to visualize.
A pump
creates pressure by pushing the water into a closed container (pipe) or a container
with limited openings (pipe with sprinkler nozzles or trickle emitters) so it
is contained under a force.
Pressure changes in a system
by friction losses or by elevation changes.
Pipe size is a factor only in that
the water velocity is faster for a given flow rate for smaller pipe diameters .
Remember that friction loss is greater for high water velocities.